Comments on: AskPablo: Water Heater vs. Stove

By: Rob Bernier

Rob Bernier — Fri, 01 May 2009 09:57:19 +0000

Hi Pablo,
I agree, but don’t like either way. The Stovetop with a conventional pot waists lots of heat because it doesn’t use a good heat exchanger. My electric hot water kettle uses electricity for heating another waist. Turning on the water to drain and warm the pipes, you have proven to be really inefficient.
I would like the following:
1) A very efficient heat extraction kettle for my stove. A folded copper heat exchanger on the bottom of the pot should extract a high percentage of the heat from the burner. I have seen an old one, but I can’t find one now.
2) A hot water on tap that doesn’t waste any water, and uses my efficient hot water heater to make it hot.
a) This is an interesting problem. The person who answers it will save billions of gallons of water, and mega watts of power.
b) I have an idea that I think will work. I am going to prototype it and see how it works.
c) I have seen the type you can buy at home depot, the flaw is that they cycle often and reduce the efficiency of your hot water heater by making a radiator that is as big as your hot water pipes that is continuously warming and cooling.
d) Given our energy situation, it is remarkable that our daily efficiency is limited by simple designs of systems in our lives that are far from optimized.
Thanks again for the informative site.
Rob

By: JudyBowser

JudyBowser — Tue, 13 May 2008 12:09:01 +0000

Is it cheaper to heat a kettle of cold water on my kitchenaid range large burner or use an electric kettle. Which unit uses less energy? I do not have an electric kettle and am thinking about purchasing one.

By: JudyBowser

JudyBowser — Tue, 13 May 2008 12:08:11 +0000

By: Sunny one

Sunny one — Sat, 06 Jan 2007 18:36:09 +0000

I have a friend who turns on the heater of the HW cylinder (electric) for hot water use once a week. He claims that heating from scratch once a week is more efficient than holding the water at hw temperature for a week. This is counter to my common belief that, for such a short time, turning off and reheating does not break even with holding the heat in the modern well insulated cylinder.
Any general opinion on this please. Also calculation formulas for proof!

By: Anonymous

Anonymous — Fri, 22 Dec 2006 14:27:09 +0000

Hot Water Heater? Why would you want to heat your hot water?

By: Anonymous

Anonymous — Thu, 30 Nov 2006 20:56:13 +0000

Where do you think the the “sludge ” in the bottom of the hot water tank came from…. the water of course. So would you rather drink water that had the sludge still in it or the water that has (at least some) of the sludge removed via the hot water heater.
As for cold water boiling faster than hot…I don’t think so. Conversely, there is speculation that “hot tap” water may freeze faster than “cold tap” water. The reasoning is that “cold tap” water has entrained air and/or dissolved air. Whereas water that has gone through the hot water heater has most of the air knocked out. The air acts as insulation to slow the cooling process. I do not ascribe to this theory, but I do not know if it has been empirically tested. However, if you use hot water in your ice tray, you will have very clear cubes (no air bubbles). Use cold water and have cloudy cubes (air bubbles).

By: Anonymous

Anonymous — Wed, 22 Nov 2006 11:09:49 +0000

The sludge in the bottom of a water heater is pretty disgusting. It’s recommended that you drain some of it off, using the tap at the bottom, to improve the efficiency of the water heater. But maybe it’s a good way to improve the safety of the water as well.

By: Bob

Bob — Tue, 21 Nov 2006 21:54:10 +0000

Hot water heaters have water forced out of them, not really drawn per se. This is due to the pressure differential being fed on the supply side that points pressurized water straight at the bottom of the tank forcing water out the other pipe due to an opening down stream. The water swirls in the tank quite readily due to the turbulence of water coming in and going out at significant pressure stirring up those nasty contaminants.
On the topic of heating water, I wonder how a microwave factors in on the efficiency side.

By: toocrazy

toocrazy — Tue, 21 Nov 2006 21:23:30 +0000

I once saw the sludge in the bottom of a hot water tank that was being changed for a new one. Gross! Best to get your water as fresh as possible from the cold tap.
Lead-free soldier is a more recent standard. Older pipes would have solder joints containing lead.

By: Jiltedcitizen

Jiltedcitizen — Tue, 21 Nov 2006 17:55:45 +0000

Pipe solder does not contain lead. And hot water heaters draw water from the top, not the bottom.

By: Jessica Gregory

Jessica Gregory — Tue, 21 Nov 2006 16:29:43 +0000

I would like to know if it’s more efficient to boil water in my electric kettle (I am on a 100% green electricity tariff) or boil water in a kettle on a LPG stove…

By: Bob

Bob — Tue, 21 Nov 2006 16:28:09 +0000

Yes. Toxic metals, bacteria, and other contaminants are concentrated in a hot water heater tank. The hot water also more readily leeches the lead from the pipe solder if you have copper pipes between your heater and your faucet. Google it ;)

By: Jiltedcitizen

Jiltedcitizen — Tue, 21 Nov 2006 14:59:54 +0000

LOL what? Sounds like rubbish to me. Are you talking about build up?

By: Bob

Bob — Tue, 21 Nov 2006 14:44:51 +0000

Since this came up in the context of making tea, it should be noted that it is not advisable to consume water from a standard hot water heater. Anyone interested in doing so should remove a heating element and take a tour of the inside of their tank if they have one. Legionnaires disease is another risk to this practice. I have yet to take a look into tankless water heaters though so if anyone has info there please weigh in.